So far as question of K.B.Saha judgment is concerned para 11 to 15 as quated in your reply refers the arguments preffered by Mr. Somnath Mukherjee counsel for appellant. observation of Hon'ble Supreme Court is in Para 17 which is as follows:
"17. As we have already noted that under the proviso to Section 49 of the Registration Act, an unregistered document can also be admitted into evidence for a collateral fact/collateral purpose, let us now look at the meaning of "collateral purpose" and then ascertain whether Clause 9 of the lease agreement can be looked into for such collateral purpose. In Haran Chandra Chakrvarti v. Kaliprasanna Sarkar AIR 1932 Cal 83(2), it was held that the terms of a compulsorily registrable instrument are nothing less than a transaction affecting the property comprised in it. It was also held that to use such an instrument for the purpose of proving such a term would not be using it for a collateral purpose and that the question as to who is the tenant and on what terms he has been created a tenant are not collateral facts but they are important terms of the contract of tenancy, which cannot be proved by admission of an unregistered lease-deed into evidence."
After considering a series of judgments Hon'ble Court held as follows:
21. From the principles laid down in the various decisions of this Court and the High Courts, as referred to hereinabove, it is evident that:
1. A document required to be registered, if unregistered is not admissible into evidence under Section 49 of the Registration Act.
2. Such unregistered document can however be used as an evidence of collateral purpose as provided in the Proviso to Section 49 of the Registration Act.
3. A collateral transaction must be independent of, or divisible from, the transaction to effect which the law required registration.
4. A collateral transaction must be a transaction not itself required to be effected by a registered document, that is, a transaction creating, etc. any right, title or interest in immoveable property of the value of one hundred rupees and upwards.
5. If a document is inadmissible in evidence for want of registration, none of its terms can be admitted in evidence and that to use a document for the purpose of proving an important clause would not be using it as a collateral purpose.
22. In our view, the particular clause in the lease agreement in question cannot be called a collateral purpose. As noted earlier, it is the case of the appellant that the suit premises was let out only for the particular named officer of the respondent and accordingly, after the same was vacated by the said officer, the respondent was not entitled to allot it to any other employee and was therefore, liable to be evicted which, in our view, was an important term forming part of the lease agreement. Therefore, such a Clause, namely, Clause 9 of the Lease Agreement in this case, cannot be looked into even for collateral purposes to come to a conclusion that the respondent was liable to be evicted because of violation of Clause 9 of the Lease Agreement. That being the position, we are unable to hold that Clause 9 of the Lease Agreement, which is admittedly unregistered, can be looked into for the purpose of evicting the respondent from the suit premises only because the respondent was not entitled to induct any other person other than the named officer in the same.
So far as question of Kalavakurti Venkata Subbaiah's judgment is concerned, facts are very much different. This case relates with registration of sale deed after its execution not the specific performance of contract.